1. Field of the Invention
This invention relates to semiconductor integrated circuits and, more particularly, to the topology and structure of oscillators manufactured on semiconductor integrated circuits.
2. Description of the Related Art
Many wireless communication devices such as mobile telephones, for example, employ a number of integrated circuits (ICs) to perform various functions. One such function is the generation of high frequency signals for use during transmission and reception. As such, some communication devices may include one or more frequency synthesizer circuits such as a phase locked loop (PLL), for example, to generate the desired high frequency signals.
A frequency synthesizer typically includes a controlled oscillator circuit, such as voltage-controlled oscillators (VCO), for example, which may be used within the control loop of a synthesizer. It may be generally desirable to integrate the oscillator circuit with the other components of the frequency synthesizer onto a single IC. However, depending on various factors such as operating frequency and fabrication technology, for example, it may be difficult to implement certain oscillator circuits on an IC.